Supported bimetallic hydrogenation catalysts treated by non-thermal plasmas

Abstract

Non-thermal plasma (NTP) may be an effective and clean way for enhancing catalyst performance. The paper aims to treat the surface of catalysts by different NTP techniques. Here, radio-frequency (RF) plasma jet, dielectric barrier discharge (DBD), and spark discharge are used to treat supported bimetallic hydrogenation catalysts (i.e., Mo-Ni sulfide/γ-Al2O3 and Mo-Co oxide/γ-Al2O3) in ambient air. Surface representations of the virgin and NTPs treated catalysts show that the surface morphology, chemical states and functional groups change remarkably after NTPs treatment. The catalyst’s surface become smoother after RF plasma jet treatment, but rougher after DBD or spark discharge treatment, compared with the virgin case. The heavy particles (i.e., Ar metastable states) in RF plasma jet, high-energy electrons in DBD, and heat in spark discharge play major roles in the plasma-catalyst interactions, respectively. The evident promotion of Mo chemical valence by the oxidation of O atoms happens after DBD treatment, which indicates that DBD may be an effective way to regulate Mo chemical valence. The MoS2 layers of the Mo-Ni sulfide/γ-Al2O3 catalyst are severely destroyed as the MoS2 Raman spectrum disappear after RF plasma jet treatment. The paper provides guidance for structure regulation of catalyst surfaces by NTPs.